如何在Python中实现__slots__? [英] How is __slots__ implemented in Python?

问题描述

• __slots__ 如何在Python中实现?
• 这是否显示在 C接口?
• 如何通过

• How is __slots__ implemented in Python?
• Is this exposed in the C interface?
• How do I get __slots__ behaviour when defining a Python class in C via PyTypeObject?

推荐答案

创建Python类时，默认情况下它们具有__dict__，您可以在它们上设置任何属性.插槽的重点是不创建__dict__来节省空间.

When creating Python classes, they by default have a __dict__ and you can set any attribute on them. The point of slots is to not create a __dict__ to save space.

相反，在C接口中，扩展类默认情况下没有__dict__，而您必须显式地添加一个扩展类并添加getattr/setattr支持来处理它(尽管幸运的是，有一些方法可以做到这一点) PyObject_GenericGetAttr和PyObject_GenericSetAttr已经存在，所以您不必实现它们，只需使用它们即可.(有趣的是，还没有PyObject_GenericDelAttr，但我不确定这是怎么回事.(我应该停止嵌套括号了)这样(或不这样))).

In the C interface it's the other way around, an extension class has by default no __dict__, and you would instead explicitly have to add one and add getattr/setattr support to handle it (although luckily there are methods for this already, PyObject_GenericGetAttr and PyObject_GenericSetAttr, so you don't have to implement them, just use them. (Funnily there is not PyObject_GenericDelAttr, though, I'm not sure what that is about. (I should probably stop nesting parenthesis like this (or not)))).

因此，不需要插槽，对于扩展类型也没有意义.默认情况下，您只允许您的getattr/setatttr方法仅访问类具有的那些属性.

Slots therefore aren't needed nor make sense for Extension types. By default you just let your getattr/setatttr methods access only those attributes that the class has.

关于其实现方式，代码位于 typeobject.c 中，这几乎只是一个问题:如果对象具有__slots__属性，请不要创建__dict__.非常令人兴奋.:-)

As for how it's implemented, the code is in typeobject.c, and it's pretty much just a question of "If the object has a __slots__ attribute, don't create a __dict__. Quite unexciting. :-)

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